as the currently used 'Dokuwiki' does not support the documentation for
different versions I have inserted additional version info in the description of
elements and attributes. This version info using the template 'vers' highlights
the info text with green background.

Currently there are the following texts used:

- "after version 2.0"
The entire element was introduced after release of version 2.0

- "> 2.0"
The attribute was changed or updated after release of version 2.0

- "deprecated with 2.1"
The element or attribute will be considered as deprecated with the release of
version 2.1 or later and will be removed with next main release (3.0).